My tread section is made of poplar plywood. I chose poplar over pine because it is a much harder wood and is less likely to warp. I purchased the plans for the Tread Section from Bermuda Triangle Engineering.
I cut out the soil sampler door opening and cut a 1/4 in. thick styrene plastic door. I drilled a hole in both sides of the door near the top. I inserted a 4d finishing nail into each hole. These will act as the hinge. I then cut off the heads of the nails.
Here's a picture of the solenoid on the inside of the door. When powered, it rotates about 30 deg. I cut a rod to the right length and connected it to the inside of the door with a pivoting hinge. Now I need to work on the actual Soil Sampler mechanism.
Well, I canned the rotary solenoid and went with a spring loaded door. I scrounged up a lead screw and mounted the soil sampler to it. I am using a stepper motor that is controlled by a Basic Stamp processor board. Using a stepper motor allows me to change direction of the motor without using a motor controller board. It also monitors the two limit switches and controls the timing of everything. UPDATED - SEE BELOW
I glued a piece of styrene to the front of the right tread section. I used the Wood Goop and it seemed to soften the styrene so I had many areas to fill with Bondo to get the surface smooth. It came out pretty good after all the filling and sanding. Now just three more sides to go.
I've ignored the tread section for over a year as I worked on the torso and the internal electronics. I decided that I had better get it painted before the cold weather sets in. Last weekend I textured it. It came out pretty good. A few spots needed some extra texturing to cover a few imperfections. It is suppose to be 90 this weekend (unheard of in upstate NY in September), so I hope to do some painting.
The tread section is finally painted. I installed several of the wheels and moved everything down to the shop in my basement. It seems that we had 80 deg. weather at the beginning of October and 40 deg. weather at the end. Nothing more will be accomplished in the garage until next year. I now need to re-install the soil sampler mechanism.
Here's a shot of the underside. Not all of the wheels are installed here. I need to thank my brother Pat, who had some of my wheels turned down to the proper size. He's the Mechanical Engineer in the family and had the know-how/connections to get them done properly. So, if you're ever in the market for an air tool, you can't beat Ingersoll-Rand air tools. (Shameless Plug).
I've started wiring the primary (120 V ac) circuit inside the tread section. I've used two terminal blocks. The one on the left will have the Line and Neutral wires. The small one on the right will have the safety ground. The small black box is a surge suppressor. I don't want any lightning strikes damaging my Environmental Control Robot.
I mounted the two power supplies in the left tread section. This is a picture from the top looking down. The closest power supply is the 5 V dc supply and the bottom, open frame power supply is the 12 V dc supply. It is not fully wired in this picture.
Here's a side shot of the 12 V dc power supply. I wanted to build in some trouble shooting features so I added this test panel. It has test points for both the 5 V & 12 V as well as status lights to tell me if the voltage is present. I have also added the wire harness in this picture.
I've decided that the Stepper Motor that powers the Soil Sampler drive screw is not fast or strong enough. I've replaced it with a larger, dc motor. This means I had to reprogram the controller since this motor works differently than the stepper motor. Also, I added an H-bridge so I can control the direction of the motor. I'm using the same H-bridge made by National Semiconductor (LMD 18200) that I used for controlling my torso rotation. I build a single motor controller on a bare perf-board. There are very few support components in the circuit and it gives me complete control of both the direction of the motor and the speed. This is a great motor driver.
This picture is a little cluttered but you can see the Basic Stamp board at the top and the H-bridge board in the center. To the right of the Stamp board is the transistor board that drives the rotating head of the soil sampler. I also added a "homing" feature to the control software. On power up, if the Soil Sampler is not in the up position, it will start moving up until it is. I found this a nice feature because during the development of the circuit & software, sometimes I would power it down before it had completed it's "soil sampling" cycle. Also, this means I know it is in the home position before I start each soil sampling cycle.
I interfaced the Soil Sampler circuitry to my Infrared received circuit board. I can now start the soil sampling process with the touch of a button. Also, I added a 5 second "power up" wait period before it starts looking for the signal from the IR circuit board. I found that the Soil Sampler circuit would sometimes activate when powering up the entire robot. It appears that all of the circuit do not come on line at the same time (which makes sense) so some initial logic signals are misread. At least that's the story I'm sticking with. The 5 second delay solved my problem. The remote is an off-the-shelf Radio Shack universal remote. I programmed it to send the standard SONY signals, which is what my IR Interface circuit board understands. Update - I've nix'd the IR remote for a RF remote that worked out much better. See my Remote Control page.
They look great and appear very durable. At this same time I found the loose wire going to the soil sampler motor that prevented it from operating at Wonderfest. I hadn't really looked until now, but I'm glad it was something simple and obvious.